1. Field of the Invention
The present invention relates to method and apparatus for continuously making articles such as bags or the like preferably from a folded double layer web of thermosealing material, and for then accumulating a predetermined number of articles into groups before discharging the groups of articles at a fixed location.
2. Description of the Prior Art
Rotary side weld bag machines which include a large continuously rotating drum are known in the art. United States Van Der Meulen Application Serial No. 539,943 discloses a continuously driven rotary bag machine having a large diameter bag making drum with a plurality of axially extending sealing pads on its periphery. A rotary sealing head having a pair of diametrically opposed heat sealing and severing bars thereon is driven in timed relation with the drum causing the bars to register with the sealing pads having a lightly tensioned folded web of thermosealing material passing therebetween. The sealing bars seal both sides of the bags and sever each bag from the web. The web is drawn from a supply roll advanced through a pair of draw rolls into a loop forming device.
The loop forming device includes a pair of idler rolls, and a vertically reciprocated roll which is moved upwardly against the lightly tensioned web. The stroke of the reciprocating roll is adjustable relative to the idler rolls so as to engage and push the web upwardly a predetermined distance relative to the two idler rolls shortly after each bag is severed from the web. This loop forming device is incorporated because the feed roll surface velocity is always less than the surface velocity of the bag making drum. An appropriate size loop of web is therefore produced and allowed to pay out at a time which will assure that during the sealing period the web velocity and seal pad surface velocity are matched and web tension is minimized.
The web drawing or feed rolls are preferrably driven via an adjustable drive ratio device or by other means permitting change of driving ratio. The drive ratio setting determines how much web will be fed per cycle of the bagmaker and thus establishes the width of the bag that will be produced. This web feeding or bag width adjustment also determines how much the web leading edge will slip rearwardly on the drum surface during each bag making cycle.
The web is maintained on the drum by vacuum, and after the bags have been formed they are blown outwardly from the bag making drum against a plurality of spaced belts which are driven at the same speed as and follow the periphery of the drum. A suction roll and an underlying belt then aid in discharging the completed bags from the prior art machine. No device is disclosed for accumulating and stacking the finished bags. The disclosure of this application is incorporated by reference herein, which application is licensed by the assignee of the present invention.
One important object of the present invention is to accumulate and stack bags in a manner which minimizes air entrapment between bags by pressing or rolling the new bags into accumulating groups and subsequently pressing or rolling the accumulated groups of bags onto a stack receiving device.
Another object of the present invention is to provide a device for accumulating and stacking finished bags which will give time for processing and/or transferring groups of bags without requiring the interruption or slowing of the bag making cycle. U.S. Pat. No. 3,105,422 Simpson et al which issued on Oct. 1, 1963 and is assigned to the assignee of the present invention discloses a bag stacking mechanism. The bag stacking mechanism includes a rotary accumulating drum which receives bags from spaced belts partially trained around and moving at the same peripheral speed as the drum. The leading edge of a predetermined number of bags enter between the fingers of a movable jaw and a stationary jaw both of which rotate with a drum one revolution for each bag being accumulated. Cam operated means are provided to open and close the movable jaws, and other cam means are provided to clamp the bags to the jaws and to subsequently push the leading edges of the accumulated bags out of the rotary drum. However, the drum includes only one set of clamp jaws and is not reciprocated during the bag accumulating operation as in the present invention.
U.S. Pat. No. 3,431,828 Crawford et al which issued on Mar. 11, 1969 and is assigned to the assignee of the present invention discloses an intermittently driven wicket conveyor of the general type disclosed in the preferred embodiment of the present invention for receiving groups of bags from the accumulating mechanism of the present invention. The disclosure of this Crawford et al patent is incorporated by reference herein.